The present invention relates to a method for manufacturing a semiconductor device.
In order to manufacture semiconductor devices that have been getting smaller, patterns have also become smaller. Research has been made to develop resist and exposers for obtaining fine patterns.
In exposers, although KrF (at 248 nm) or ArF (at 193 nm) as an exposure light source have been applied to exposure process, attempts have been made to use short wavelength light sources such as F2 (at 157 nm) or EUV (at 13 nm) to increase numerical apertures (NA).
However, when new light sources such as F2 or EUV are applied, a new exposer is required, which results in increasing manufacturing costs. Also, the increase of numerical apertures degrades a focus depth width.
Recently, an immersion lithography process has been developed with an immersion solution having a high refractive index. However, it is difficult to apply the immersion lithography process to mass production.
Although fine patterns having a resolution beyond lithography limits are formed by a dual exposure method, it is difficult to secure margins of overlapping and arrangement degrees, which results in excessive consumption of cost and process time.